Created attachment 565106[details][diff][review]
patch
Accesses on properties with watchpoints were being optimized, where the optimizations bypassed the watchpoint handler. The intent here was to mark watched type properties as configured (as if they had been turned into a setter, made read-only, etc.), which inhibits optimizations on them. This was done for properties watched on objects with non-singleton types, but when lazily generating type properties for singleton objects the watchpoints were not taken into account.